1. Preliminary quick judgment: disconnect all modules of the module, only supply the module 5v (that is, vcc is connected to 5v, gnd ground), then short the module's ck port to ground, and then measure the out-to-ground voltage, which should be 4.5 v around, then measure the DO / RX port to ground voltage, should be about 0v, if the voltage is consistent, the module is 99% normal.

2. Complete test judgment: use the test circuit diagram provided by the shop to build a circuit, give the 89c51 single-chip computer into the hex test program provided by the store, then connect the computer with the serial cable, run the serial port assistant on the computer, you can receive the test circuit. The reading is reported and the reading is normal, indicating that the module is normal. See the test chart below for details.